Harford County has become the final Maryland jurisdiction to approve a state-mandated plan for trash recycling.

At the same time, county officials are asking private haulers to encourage residents to recycle by offering economic incentives.

"Since we are not in the trash business, we must rely on the haulers to promote this thing," said Larry Klimovitz, county director of administration.

The council voted 6-1 early yesterday to approve the plan, which calls for private haulers to offer once-a-week curbside collection of recyclables.

To pay for the effort, which will cost $3 million a year at the outset, the plan establishes a $35-a-ton fee that haulers must pay to deposit trash at the county incinerator or landfill.

Haulers will not be charged for depositing recyclables at a county transfer station.

From the transfer station, recyclables will be hauled to private processors, who will then sell the material to manufacturers.

Councilman Robert S. Wagner, R-District E, was the lone dissenter.

He said the county was jumping into an expensive program without securing markets for recycled items.

Harford residents living outside the municipal borders of Aberdeen, Bel Air and Havre de Grace contract privately with haulers for trash collection.

At least one hauler, McKenzie Recycling and Sanitation of Baldwin, already is contemplating an incentive system.

In theory, McKenzie's 3,500 customers would be asked to buy stickers for their trash containers.

They would be charged less -- or nothing at all -- for stickers to be placed on containers for recyclables.

"They are only going to pay for the trash they generate," said John McKenzie, the company's owner.

McKenzie has been offering curbside recycling to its customers at no charge for about a year. With approval of the county recycling plan, the company hopes to establish a full "variable-rate" collection system, as it's known in the solid-waste industry, as early as April or May.

Harford's plan also calls for residents to use blue bags for recyclables to distinguish the material from ordinary trash.

David Bullock, vice president of GBB Inc., a Falls Church, Va., consulting firm that helps local governments deal with waste, said there are dozens of variable-rate collection systems across the country.

He said they're used by jurisdictions such as Harford with an extensive system of private haulers, or for recycling programs that aren't government-sponsored.

Such programs are operating in Carlisle, Pa., and surrounding areas near Harrisburg, as well as in parts of New Jersey and Florida and elsewhere. Bullock was not aware of another incentive system in Maryland.

State law requires Maryland counties and Baltimore to recycle 15 to 20 percent of their trash by 1994.